Car dies when there is a current draw (F.A.S.T)

[Grandnat]

Anytime I hit the brakes or turn on the headlights or roll up/down the power windows the car dies.

I logged it on FAST and noticed that when this happens the car goes pig rich. The injector pulse width goes from about 1.5 to 7!!!
(83 lb inj)


can anyone think why the injectors would hang open when there is a current load applied to the car?

I hooked the car up to a battery charger and tested it and it still died anytime I hit the brakes. so it is not related to a bad alternator or battery as far as I can tell.

I checked all the grounds I know of.... could this be a ground on the fast harness itself that I forgot?


p.s. I still ahve a power master brake booster, so when I hit the brakes there is a large electric load on the motor when the pump kicks in.

 

[bobc455]

I fought a low voltage issue for a long time, once I got the car's voltage up it ran much better. I had a hard time whenever the car went below 13 volts, now I maintain about 13.9 volts and it is okay.

I suspect the problem would be worse with 83# injectors- mine are only 36#.

I don't like the voltage correction scheme that the FAST uses. A 7 ms PW will make you pig rich, for sure- something sounds goofy there. How old is your system?

-Bob Cunningham

 

[Grandnat]

I just got the car running.... got the F.A.S.T less than a year ago, but just installed it recently

so it is new.

 

[RickWI]

What is the running voltage and what does the voltage do when it dies?

 

[Otto J]

Sure you dont have a bad altenator?

 

[Grandnat]

I will try and put up a screenshot of one of the logs.

my voltage is ~13.6 at idle.

I will check when I get home and see if it dips at all when I apply current load.... I assume that it will and I also assume that thats normal.

can anyone tell me how much voltage drops when they apply the brakes? or turn on the headlights

I know it will be for just a frame or two until it corrects.

 

[norbs]

SOmethings wrong here.........

My car has 83's and i am drawing 130 amps from the alternator with the a/c on and the headlights on, and the injector pule width does not change , maybe .1 ms. Run 10 awg wires from the battery directly + , and - run it through the firewall near the wheel well on the right side near where the factory harness goes., yes you have to pull the wheel well out a bit and jack the car up. ALso you should put a fuse within 12" of the battery connection for safety sake, about 20 amps is good.

 

[Chuck Leeper]

WTF???

Originally posted by norbs
SOmethings wrong here.........

My car has 83's and i am drawing 130 amps from the alternator with the a/c on and the headlights on, and the injector pule width does not change , maybe .1 ms. Run 10 awg wires from the battery directly + , and - run it through the firewall near the wheel well on the right side near where the factory harness goes., yes you have to pull the wheel well out a bit and jack the car up. ALso you should put a fuse within 12" of the battery connection for safety sake, about 20 amps is good.

Talk about something being wrong!!
Are those Canadian Amps??

 

[norbs]

They are USA amps! Measured on a USA built insrument which is very accurate. I have the 200 amp alternator and the engine almost dies as it becomes loaded. The fans draw 54 amps, water pump 6, fuel pump 6 amps, then you have the headights about 20 amps and the ingnition system and felpro idling about 10 amps. The rest goes into charging the battery. I will gladly make a video of this if no one bel;ieves me still!

 

[S2V6RACER]

I wouldn't be surprized. I am curious how much amperage I am pulling at idle with the fans on.

 

[RickWI]

Most alternators are set to put out over 14 volts at idle, if the load on the alternator is not exceeding rated output, at idle of course. With a good charging and wiring system you should not see a drop in voltage when you hit the brakes. You may have a bad votage regulator, diode out on the alternator, poor grounds or simply a bad battery.

 

[Grandnat]

*****UPDATE ----FIXED IT!!!!!******

Well it turns out that the problem was not electrical at all!

The AE VS MAP rate of change chart was far too agressive.

Basically when a large current draw happened the alternator kicked in and put a small load on the motor.

This load changed the MAP reading enough and at a rate of change sufficient to have the computer request an additional 4% Duty cycle. which caused my motor to sputter and die.

took me a while to figure it out... and I wasted alot of time checking grounds.


But all is well ......for now!

 

[bobc455]

Good to hear you got it worked out. I am a little surprised at the answer, but we always learn something new.

Originally posted by norbs . The fans draw 54 amps

You must have one mega fan arrangement! I run twin puller fans and one pusher fan through a single 30 amp fuse...

-Bob Cunningham

 

[Chuck Leeper]

More cannuck mumbojumbo!!

Originally posted by bobc455
Good to hear you got it worked out. I am a little surprised at the answer, but we always learn something new.



You must have one mega fan arrangement! I run twin puller fans and one pusher fan through a single 30 amp fuse...

-Bob Cunningham

My thots exactly, Bob!! Must be metric amps....

 

[norbs]

When you buy a real fan, you get real amps! Most of the fans except the spals and derales are way over rated. Mine are rated 4000 cfm and i still do not have enough cooling with the a/c on.

 

[ijames]

I think the best bang for the buck in fans has to be the Ramchargers dual fan setup for $80. On a car with a stock location intercooler (no frontmount) and a/c condenser I've seen a shop rag dropped in line with the front edge of the bumper get sucked over against the grill .

 

[kidrick]

Grnadnat,

I may be having the same problem. What where your old AE vs. MAP rate of Change numbers and what did you adjust them to to fix the stalling? Mine start at 0 and go up to 3.98.

 

[Grandnat]

I was using the one on the demo program.

and that sounds about right.

I altered it so it didn't rise as aggressively and it toped out below 3.

 

[Louie L.]

The Spal fans are the only ones that are not overrated. DERALE is junk andnot even in the same group as Spal.

On the mentioned subject the FAST correction factor is sometimes too much which cause ideling issues especially with big injectors and sudden current draws.At night with the headlights on and the Spals kicking on, my car will stumble but not die.

 

[Grandnat]

Originally posted by Louie L.
The Spal fans are the only ones that are not overrated. DERALE is junk andnot even in the same group as Spal.

On the mentioned subject the FAST correction factor is sometimes too much which cause ideling issues especially with big injectors and sudden current draws.At night with the headlights on and the Spals kicking on, my car will stumble but not die.

there you go!!

thanks Louie

I had the same problem and I use SPAL fans as well (they kick ass)


changing the MAP vs AE cured it all.